在typescript中创建某个类型的变量

let num: number = 123;
let str: string = "Hello, TypeScript!";
let bool: boolean = true;

let arr: number[] = [1, 2, 3];
let tuple: [string, number] = ["foo", 42];

interface Person {
    name: string;
    age: number;
}

let person: Person = {
    name: "Alice",
    age: 30
};

type UserId = string;

let userId: UserId = "user123";

function identity<T>(arg: T): T {
    return arg;
}

let result: number = identity<number>(123);

type StringOrNumber = string | number;

let value: StringOrNumber = "hello"; // 或者 let value: StringOrNumber = 123;

interface A {
    a: string;
}

interface B {
    b: number;
}

type AB = A & B;

let ab: AB = {
    a: "test",
    b: 42
};

class MyClass {
    constructor(public name: string) {}
}

let instance: MyClass = new MyClass("TypeScript");